On Juan's 26th birthday, he invested $6,500 in a retirement account. Each year thereafter, he deposited 7% more than the previous deposit. The account paid annual compound interest of 6%. How much was in the account immediately after his 35th deposit?
a) If Juan decided to wait 10 years before investing for retirement, how much would he have to invest on his 36th birthday to have the same account balance on his 60th birthday?
b) What uniform annual investment is required to achieve the same account balance?